1. Field of the Invention
The present invention relates to a positive electrode material (cathode material) which can be suitably used for a chargeable and dischargeable non-aqueous electrolyte secondary battery.
2. Description of the Related Art
It is known that a metal fluoride such as iron fluoride is used as a positive electrode active material used in a positive electrode material for a chargeable and dischargeable non-aqueous electrolyte secondary battery (see, for example, Japanese Patent Laid-Open No. 2008-130265). The iron fluoride, when used as a positive electrode active material for the non-aqueous electrolyte secondary battery, is said to be able to improve the charge and discharge characteristics such as a charge and discharge capacity and an energy density of the non-aqueous electrolyte secondary battery.
The present inventors have investigated the iron fluoride used as the positive electrode active material for the non-aqueous electrolyte secondary battery and have found that partial replacement of Fe constituting iron fluoride with atoms having an ionic radius larger than that of Fe further improves the charge and discharge capacity and the energy density. Examples of the atom having an ionic radius larger than that of Fe include Na and Co or the like.
However, further improvements in the positive electrode active material in which Fe is partially replaced with Na and Co or the like are required from the viewpoint of the power density of the non-aqueous electrolyte secondary battery.
It is thus an object of the present invention to provide a positive electrode material for a non-aqueous electrolyte secondary battery, the material having an energy density and a power density higher than those of a positive electrode material for a non-aqueous electrolyte secondary battery employing only iron fluoride as the positive electrode active material.